[doc] Update Tru64 UNIX installation documentation

[Gerald Pfeifer]

On Wed, 31 Mar 2010, Rainer Orth wrote:
> In preparation for the GCC 4.5.0 release, I'm updating the Tru64 UNIX
> installation documentation.  I'm not primarily looking for factual
> comments (although those are of course welcome, too), but more for
> suggstions on wording and markup.

It looks good from what I can tell.  Nice to see this trimmed and
old stuff removed.

Gerald